Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC293
Oxytocin Alters Spike Activity in Oxytocin Neurons
R. Dyball1, X. Jin1
1. Physiology Development and Neuroscience, Univ Cambridge, Cambridge, United Kingdom.
The neuropeptide oxytocin is not only an important reproductive hormone, but also regulates emotional and social behaviours such as anxiety and maternal bonding (see eg Broad, Curley and Keverne, 2006). To exert such effects, oxytocin must have an effect on neural behaviour. Earlier studies showed that oxytocin affected the firing frequency of oxytocin neurones in vitro (Inenaga and Yamashita, 1986) and in vivo (Jiang and Wakerley, (1995) but these studies reported increased frequency only and did not show whether it changed the information coded by the spike trains. The present investigation was based on recordings published by (Jiang and Wakerley, (1995). Its aim was to quantify, using the methods outlined by Bhumbra and Dyball (2004) and Sabatier, Brown, Ludwig and Leng (2004), any changes in the patterns of spike activity of oxytocin neurons within the SON that were induced by oxytocin (2.2 ng) injected ICV. There were significant differences in both the mean spike frequency and in the entropy of the log interspike intervals between recordings made before and after administration of oxytocin ICV (paired Student’s t-test, n = 14, P<0.001). Using Pearson’s Correlation Coefficient to assess the relationship between adjacent interspike intervals within the bursts we also found that ICV oxytocin administration significantly increased the complexity of spike coding within the bursts (paired Student’s t-test, n = 29, P<0.01). Both these effects may have been due, in part, to a depolarising action of oxytocin on the OT neurones themselves. They may also reflect more complex actions on other brain regions that modulate the inputs to the SON. Our results do however show clearly that oxytocin, acting centrally, can alter the coding capacity of neurones. It seems likely that such actions of oxytocin, operating at different sites within the brain, may contribute to the mechanism by which oxytocin modulates more complex behavioural patterns. Acknowledgements: We thank Dr Gary Bhumbra for advice and Dr JB Wakerley for permission to use the relevant digital files.
Where applicable, experiments conform with Society ethical requirements